I just bought a 550w psu (antec vp550f) and GeForce gtx 660 to put in my stock HP PC model H8 - 1210. After getting everything hooked up, I start it and it freezes on the hp screen and says "esc for startup menu" when I hit esc it takes me to a black screen with my specs and I can't do anything from there. When I put my old card back in (gt 520) that came with it everything works fine and it starts normally. Everything is connected correctly I just can't seem to get past that screen with the new gpu installed. Any advice or help would be greatly appreciated. This the first time I've tried to do any kind of upgrade like this and I've been researching other threads for hours but can't seem to figure it out. Happy to to try any ideas u might come up with. Thanks